8101 Hempstead Road (I-10 at Washington) - Houston, Texas 77008

Diagnostics and Repair – Why They Are Not The Same

How did this ever come up ???

Actual Phone Calls:

Customer: “I have fault code P3022x on my car – How much will it take to fix it ?”

Motorcars: “Not sure, we will need to see the car and take a look.”

Customer: “I have already told you what is wrong, what will you charge to fix it ?”

Motorcars: “We cannot tell you on the phone without seeing the car.”

Customer: “OK… I will take it to another shop who says they can fix it.”

Three weeks pass…….

Customer: “I had a throttle body put on my car, but the P3022x fault code is still on and I paid $875.12. What will you charge to fix it ?”

Motorcars: “We cannot tell you on the phone without seeing the car. We will need to diagnose the car’s problem ?”

Customer: “ OK… what will you charge me to look for the problem and fix it ?”

Motorcars: “We do diagnostic work by the hour and ask that we have a 3 hour floor for electrical problems. If we need more hours, we will let you know; and then we will do the needed repair work by the hour once the problem is diagnosed…..”

Customer: “ But the other shop quoted me a labor price to change the throttle body and no diagnostics. I don’t understand”.

Motorcars: “Well, they didn’t fix it, did they ?”

We have some variation of this scenario to deal with almost every day.

What most customers do not understand is that while Motorcars owns and uses five different computers for car specific specific diagnostics, these computers can only tell us the general circuit that is faulty….. it cannot tell us which wire in the bundle has chaffed, where or which connector has corroded or which ground for the circuit is compromised and not making a “good ground”.

In the above actual case, the fault code in fact indicated that the “throttle body CIRCUIT” was faulty, and the other shop replaced the throttle body and shipped the car under the assumption that the car was fixed. The fault code was gone temporarily and everyone was seemingly happy.

But, now, the fault code has returned. Why ? Because the REAL problem was not the throttle body itself. The REAL problem involved the connectors and the connector holder at the throttle body itself – the connector had corroded but coincidentally were wiggled around during installation to make a temporary good contact…. AND the connectors at the other end of the same wires that led from the ECM (the electronic control module) were growing corrosion…. AND to top it all off, the ECM wire ends were corroded INSIDE the box and the box ground was rusted….. !

So the other shop quoted the time and materials to change the “faulty” component, but did not fix the problem.

In this case, Motorcars was obliged to spend DIAGNOSTIC time to FIND the real problem…. which was impossible to see or diagnose on the phone. Often it becomes a detective job even when the car is here. The wiring must still be taken apart to find the offending wire connectors and component corrosion.

On electrical issues, Motorcars asks for a minimum of 3 hours to get started into the “diagnostic tree”. If we need more hours for diagnostics – (ie: after three hours, and we have still not found the problem, then we will stop and call the customer) – we tell the customer where we are and request more hours for additional diagnostics…. At the three hour mark, we should have a pretty good idea of what we are dealing with, but sometimes, we do not….

Once we find the problem, (and very often, we fix the problems with wire connections or grounds as we go) we can then identify the faulty part or component that we need to replace. The time to replace the faulty component plus the parts needed become “the repair” and everything leading up to identifying the needed repair, we consider to be “the diagnostics”….

Diagnostic dollars are not applied to the repair…. They are two very different skill sets and often very different times.

The cars we work on are incredibly complicated and tedious to work on because of the electrical issues caused by water incursion or faulty assembly. We do not throw a quick fix quote at the wall in hopes of quoting a repair with the easy fix…. We always ask to see the car for our diagnostics and the owner should expect to pay for the time to figure out exactly which component is faulty.

It used to be that a good mechanic could listen to a problem and pronounce the fix standing 25 feet from the car. Not these days, I am afraid.

Some times diagnostics are pretty easy – if water is pouring out of the water pump, we will need to replace the water pump…. And no diagnostics will be charged… BUT if the water pump lives BEHIND other components and engine covers and must be removed to verify the faulty water pump, then that time to confirm the water pump leak or offending water hoses is chargeable as diagnostics.

Bottom line…. Motorcars can only successfully repair your car if the problem is properly diagnosed. The owner should expect to pay for a studied and professional diagnosis as well as the cost to actually replace the offending component.



XKE 4.2 with Webers
Temperature Diagnostics
Jaguar XK8 Main Body Harness
Land Rover Relays
Testing For Valve Leaks
Instrument Cluster XK8
XKE 4.2 Engine Rebuild
Main Harness Land Rover
MGB Engine Repair

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